Heat-sensitive recording material

ABSTRACT

Disclosed is a heat-sensitive recording material containing an ultraviolet light absorber precursor which forms an ultraviolet light absorber by being irradiated with light, and a hydrogen donor.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a heat-sensitive recordingmaterial and more particularly to a heat-sensitive recording materialexcellent in lightfastness.

[0003] 2. Description of the Related Art

[0004] In recent years, heat-sensitive recording has made remarkableprogress because the recording apparatus for heat-sensitive recordingare simple, highly reliable, and maintenance-free. Examples of widelyknown heat-sensitive recording materials are a heat-sensitive recordingmaterial utilizing the reaction between an electron-donating colorlessdye and an electron-accepting compound, and a heat-sensitive recordingmaterial utilizing the reaction between a diazonium salt compound and acoupler.

[0005] However, the heat-sensitive recording material is associated witha problem that, when it is exposed to sunlight for a long time or whenit is posted on the wall in an office or the like for a long period oftime, its background becomes colored and the image portions may discoloror fade.

[0006] Japanese Patent Application Laid-Open (JP-A) No.9-1928 describesa heat-sensitive recording material which uses a precursor of anultraviolet light absorber in order to prevent the coloration of thebackground and the discoloration or fading of the image portions andexhibits excellent lightfastness and fixing performance. This precursorof an ultraviolet light absorber functions as an ultraviolet lightabsorber after it reacts due to the effect of light or heat whenirradiated with light whose wavelength is in a region necessary forfixing by irradiation with light in a photo-fixing type heat-sensitiverecording layer. For this reason, a large proportion of the light withinan ultraviolet region is absorbed by the ultraviolet light absorber andthe ultraviolet light transmittance of the heat-sensitive recordingmaterial is lowered. Therefore, the lightfastness of the heat-sensitiverecording material is enhanced.

[0007] However, if the precursor of an ultraviolet light absorber wasused alone, the problem encountered was that the efficiency of theultraviolet light absorber formation was low when the ultraviolet lightabsorber was formed by irradiation with light.

SUMMARY OF THE INVENTION

[0008] The present invention provides a heat-sensitive recordingmaterial which is excellent in lightfastness and solves the problem thatthe efficiency of the ultraviolet light absorber formation is low andthus overcomes the above-mentioned problems.

[0009] That is, the first aspect of the present invention is aheat-sensitive recording material containing an ultraviolet lightabsorber precursor which forms an ultraviolet light absorber by beingirradiated with light and a hydrogen donor. Preferably, the ultravioletlight absorber precursor is at least one kind selected from thecompounds represented by the following general formulae (1) to (4).

[0010] In the general formulae (1) to (4), m represents 1 or 2. Arepresents —SO₂—R, —CO—R, —CO₂—R, —CONH—R, —POR₁R₂, —CH₂R₃, or SiR₄R₅R₆in the general formula (1) where m is 1 and in the general formulae (2)to (4). A represents —SO₂R₇SO₂—, —CO—, —COCO—, —COR₇CO—, —SO₂—, or SO—in the general formula (1) where m is 2. X represents a hydrogen atom,an alkyl group, an alkoxy group, an aryl group, or a halogen atom in thegeneral formulae (1), (3), and (4). X represents an alkylene group,—OR₇O—, or OCOR₇CO₂— in the general formula (2). W represents a hydrogenatom, an alkyl group, an alkoxy group, an aryl group, or a halogen atomin the general formulae (1), (2), and (4). W represents —OR₇O— orOCOR₇CO₂— in the general formula (3). Y represents a hydrogen atom, analkyl group, an alkoxy group, an aryl group, or a halogen atom in thegeneral formulae (1), (2), and (3). Y represents —OR₇O—, —OCOR₇CO₂—,—CH₂CH₂CO₂R₇OCOCH₂CH₂—, —CH₂CH₂COR₇CO₂CH₂CH₂—, or CH₂CH₂CON(R₈)R₇N(R₈)COCH₂CH₂— in the general formula (4). Z represents a hydrogenatom, a halogen atom, an alkyl group, or an alkoxy group. In the groupslisted above, R represents an alkyl group or an aryl group. R₁ and R₂each represents an alkoxy group, an aryloxy group, an alkyl group, or anaryl group. R₃ represents a phenyl group bearing at least one nitro ormethoxy group as a substituent. R₄, R₅, and R₆ each represents an alkylgroup or an aryl group. R₇ represents an alkylene group or an arylenegroup. R₈ represents a hydrogen atom or an alkyl group.

[0011] It is preferable that the hydrogen donor has at least one groupselected from an aromatic OH group, an aliphatic OH group, aheterocyclic OH group, an aromatic SH group, an aliphatic SH group, aheterocyclic SH group, an aromatic NH group, an aliphatic NH group, anda heterocyclic NH group.

[0012] Another aspect of the present invention is a heat-sensitiverecording material comprising a support, a photo-fixing typeheat-sensitive recording layer, an interlayer, and a protective layer,each provided on the support, wherein at least one of these layerscontains an ultraviolet light absorber precursor and a hydrogen donor.

[0013] Still another aspect of the present invention is a multicolorheat-sensitive recording material which comprises a support and aplurality of photo-fixing type heat-sensitive recording layers providedon the support and contains an ultraviolet light absorber precursor anda hydrogen donor, wherein the photo-fixing type heat-sensitive layersdevelop the three primary colors for subtractive color mixing, i.e.,yellow, magenta, and cyan, respectively, so that full-color recordingcan be made.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Heat-Sensitive Recording Material>

[0015] The heat-sensitive recording material of the present inventioncontains at least one compound selected from the compounds representedby the following formulae (1) to (4) and a hydrogen donor.

[0016] The compounds represented by the general formulae (1) to (4) areso-called precursors of ultraviolet light absorbers and form ultravioletlight absorbers by being irradiated with light. The compoundsrepresented by the general formulae (1) to (4) are hereinafter referredto as “ultraviolet light absorber precursors” upon occasion. Theheat-sensitive recording material of the present invention contains ahydrogen donor in addition to the ultraviolet light absorber precursor.For this reason, the supply source, which supplies hydrogen to theultraviolet light absorber precursor is increased and the efficiency ofthe formation of the ultraviolet light absorber is enhanced. The term“hydrogen donor” as used in the present invention means a compound whichdonates hydrogen to the ultraviolet light absorber precursor.

[0017] (Hydrogen Donor)

[0018] Examples of the hydrogen donor include hydroquinone compounds,hydrazide compounds, hydroxy compounds, phenidone compounds, catecholcompounds, resorcinol compounds, hydroxyhydroquinone compounds,pyrrologlycinol compounds, phenol compounds, phenylhydrazide compounds,gallic acid compounds, ascorbic acid compounds, and ethylene glycolcompounds. These are described in JP-A Nos.3-191341, 3-25434,1-252953,2-302753, 1-129247, 1-227145, 1-243048,2-262649, etc.

[0019] Among the hydrogen donors listed above, preferable is a hydrogendonor (an OH group-bearing hydrogen donor) having at least one groupselected from an aromatic OH group, an aliphatic OH group, and aheterocyclic OH group; a hydrogen donor (an SH group-bearing hydrogendonor) having at least one group selected from an aromatic SH group, analiphatic SH group, and a heterocyclic SH group; or a hydrogen donor (anNH group-bearing hydrogen donor) having at least one group selected froman aromatic NH group, an aliphatic NH group, and a heterocyclic NHgroup.

[0020] Examples of the OH group-bearing hydrogen donor include compoundsrepresented by “heterocycle-OH”, “R¹⁰—COOH”, etc., wherein R¹⁰represents an aliphatic group, an aromatic group, or a heterocyclicgroup. Examples of R¹⁰ include octyl, dodecyl, octadecyl, 2-ethylhexyl,oleyl, phenyl, naphthyl, tolyl, cyclohexyl, and pyridyl groups. Examplesof the OH group-bearing hydrogen donor include hydroquinone andderivatives thereof, phenol and derivatives thereof, hindered phenol andderivatives thereof, tocopherol and derivatives thereof, and ascorbicand derivatives thereof. The OH group-bearing hydrogen donor may havetwo or more OH groups. Preferred specific examples of the OHgroup-bearing hydrogen donor are given below.

[0021] Examples of the SH group-bearing hydrogen donor include mercaptocompounds represented by “heterocycle-SH” and compound represented by“R¹¹—COSH”, etc., wherein R¹¹ represents an aliphatic group, an aromaticgroup, or a heterocyclic group. Examples of R¹¹ include octyl, dodecyl,octadecyl, 2-ethylhexyl, oleyl, phenyl, naphthyl, tolyl, cyclohexyl, andpyridyl groups. Examples of the SH group-bearing hydrogen donor include2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole,etc. The SH group-bearing hydrogen donor may have two or more SH groups.

[0022] Examples of the NH group-bearing hydrogen donor include compoundsrepresented by “heterocycle-NH—R¹²”, R¹³—CONH—R¹²”, etc., wherein R¹²represents a hydrogen atom, an aliphatic group, an aromatic group, or aheterocyclic group and R¹³ represents an aliphatic group, an aromaticgroup, or a heterocyclic group. Examples of R¹² include a hydrogen atom,and octyl, dodecyl, octadecyl, 2-ethylhexyl, oleyl, phenyl, naphthyl,tolyl, cyclohexyl, and pyridyl groups. Examples of R¹³ include octyl,dodecyl, octadecyl, 2-ethylhexyl, oleyl, phenyl, naphthyl, tolyl,cyclohexyl, and pyridyl groups. Examples of the NH group-bearinghydrogen donor include primary amines and derivatives thereof, secondaryamines and derivatives thereof, and compounds having a urea linkage. TheNH group-bearing hydrogen donor may have two or more NH groups.Preferred specific examples of the NH group-bearing hydrogen donor aregiven below.

[0023] Besides the hydrogen donors listed above, it is possible to usehydrogen donors such as an ester (e.g., triethanolamine acetate)prepared by esterification of an amine having a hydroxyalkyl group as asubstituent, an ether having an oxyalkylene group (e.g.,2-benzyloxynaphthalene and 1,2-diphenoxyethane), etc.

[0024] Preferably, the heat-sensitive recording material of the presentinvention comprises a support and a photo-fixing type heat-sensitiverecording layer and, if necessary, an interlayer and a protective layermay also be provided on the support. The hydrogen donor may beincorporated in any of these layers, with the proviso that the hydrogendonor is incorporated in the layer containing a compound represented byany of the general formulae (1) to (4). In some case, for example, theheat-sensitive recording material may have an additional layer such as alight transmittance controlling layer which contains the hydrogen donorand the ultraviolet light absorber precursor.

[0025] The proportion of the hydrogen donor is preferably 1 to 1000% byweight, more preferably 5 to 300% by weight, and most preferably 10 to100% by weight relative to the compound represented by any of thegeneral formulae (1) to (4). If the proportion is within the range of 1to 1000% by weight, the compounds represented by the general formulae(1) to (4) can be converted efficiently into ultraviolet lightabsorbers.

[0026] (Compounds Represented by the General Formulae (1) to (4))

[0027] In the present invention, the compounds represented by thegeneral formulae (1) to (4) function as precursors of ultraviolet lightabsorbers. These compounds do not function as ultraviolet lightabsorbers before the irradiation with light in the wavelength regionnecessary for fixing. For this reason, the light transmittance of thephoto-fixing type heat-sensitive recording layer containing theprecursor of ultraviolet light absorber is high. The precursor ofultraviolet light absorber sufficiently transmits the light in thewavelength region necessary for fixing and does not hinder the fixing ofthe photo-fixing type heat-sensitive recording layer. In addition, thevisible light transmittance in the photo-fixing type heat-sensitiverecording layer is also high.

[0028] After the compounds represented by the general formulae (1) to(4) are irradiated with light in the wavelength region necessary forfixing by light in the photo-fixing type heat-sensitive recording layerand react due to the effect of light or heat, the compounds function asultraviolet light absorbers. For this reason, the light in anultraviolet region is mostly absorbed by the ultraviolet light absorber.Accordingly, the ultraviolet light transmission of the light in anultraviolet light region to the heat-sensitive layer is reduced and thelightfastness of the heat-sensitive layer is enhanced. On the otherhand, since the ultraviolet light absorber does not absorb the visiblelight, the visible light transmittance in the heat-sensitive layer doesnot change substantially.

[0029] In the general formulae (1) to (4), m represents 1 or 2.

[0030] A represents —SO₂—R, —CO—R, —CO₂—R, —CONH—R, —POR₁R₂, —CH₂R₃, orSiR₄R₅R₆ in the general formula (1) where m is 1 and in the generalformulae (2) to (4). A represents —SO₂R₇SO₂—, —CO—, —COCO—, —COR₇CO—,—SO₂—, or SO— in the general formula (1) where m is 2.

[0031] X represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (3), and (4).X represents an alkylene group, —OR₇O—, or OCOR₇CO₂— in the generalformula (2).

[0032] W represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (2), and (4).W represents —OR₇O— or OCOR₇CO₂— in the general formula (3).

[0033] Y represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (2), and (3).Y represents —OR₇O—, —OCOR₇CO₂—, —CH₂CH₂CO₂R₇OCOCH₂CH₂—,—CH₂CH₂OCOR₇CO₂CH₂CH₂—, or CH₂CH₂CON(R₈)R₇N(R₈)COCH₂CH₂— in the generalformula (4).

[0034] Z represents a hydrogen atom, a halogen atom, an alkyl group, oran alkoxy group.

[0035] In the groups listed above, R represents an alkyl group or anaryl group. R₁ and R₂ each represents an alkoxy group, an aryloxy group,an alkyl group, or an aryl group. R₃ represents a phenyl group bearingat least one nitro or methoxy group as a substituent. R₄, R₅₁ and R₆each represents an alkyl group or an aryl group. R₇ represents analkylene group or an arylene group. R₈ represents a hydrogen atom or analkyl group.

[0036] Among the substituents listed above, the alkyl group may be astraight-chain alkyl group or a branched alkyl group. Further, the alkylgroup may have an unsaturated bond. Furthermore, the alkyl group maybear a substituent such as an alkoxy group, an aryloxy group, analkoxycarbonyl group, an aryloxycarbonyl group, an aryl group, ahydroxyl group, or the like. The aryl group may further bear asubstituent such as an alkyl group, an alkoxy group, or a halogen atom.

[0037] Among the substituents listed above, the alkylene group may be astraight-chain alkylene group or a branched alkylene group. Further, thealkylene group may contain an unsaturated bond, an oxygen atom, a sulfuratom, or a nitrogen atom. Furthermore, the alkylene group may bear asubstituent such as an alkoxy group, a hydroxyl group, an aryloxy group,or an aryl group.

[0038] Among the substituents listed above, the arylene group mayfurther bear a substituent such as an alkyl group, an alkoxy group, ahalogen atom, or the like.

[0039] Among the substituents represented by X, Y, or W, a hydrogenatom, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having1 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, afluorine atom, a chlorine atom, and a bromine atom are preferable. Amongthese substituents, a hydrogen atom, an alkyl group having 1 to 12carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a phenylgroup, and a chlorine atom are particularly preferable.

[0040] Among the substituents represented by Z, a hydrogen atom, achlorine atom, a fluorine atom, an alkyl group having 1 to 12 carbonatoms, and an alkoxy group having 1 to 12 carbon atoms are preferable.Among these substituents, a hydrogen atom, a chlorine atom, an alkylgroup having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6carbon atoms are particularly preferable.

[0041] Among the substituents represented by R, an alkyl group having 1to 18 carbon atoms and an aryl group having 6 to 18 carbon atoms arepreferable. Among these substituents, an alkyl group having 1 to 12carbon atoms and an aryl group having 6 to 12 carbon atoms areparticularly preferable.

[0042] Among the substituents represented by R₁ or R₂, an alkoxy grouphaving 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbonatoms, an alkyl group having 1 to 12 carbon atoms, and an aryl grouphaving 6 to 12 carbon atoms are preferable.

[0043] Among the substituents represented by R₃, a 2-nitrophenyl group,a 3,5-dimethoxyphenyl group, and 3,4,5-trimethoxyphenyl group arepreferable.

[0044] Among the substituents represented by R₄, R₅, or R₆, an alkylgroup having 1 to 12 carbon atoms and an aryl group having 6 to 12carbon atoms are preferable. Among these substituents, an alkyl grouphaving 1 to 8 carbon atoms and a phenyl group are particularlypreferable.

[0045] In a so-called bis-structure having two benzotriazole rings inone molecule, an alkylene group having 1 to 12 carbon atoms or anarylene group having 6 to 12 carbon atoms is preferable as thesubstituent represented by R₇ and a hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms is preferable as the substituent representedby R₈.

[0046] Among the substituents represented by A, —SO₂R is particularlypreferable.

[0047] Specific examples of the above-listed substituent are givenbelow, though it should be understood that the present invention is notrestricted to these examples.

[0048] Among the substituents represented by X, Y, or W, monovalentsubstituents include a hydrogen atom, a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,a sec-butyl group, a t-butyl group, a pentyl group, a hexyl group, anoctyl group, a decyl group, a dodecyl group, an allyl group, a 2-butenylgroup, a benzyl group, an α-dimethylbenzyl group, a methoxy group, anethoxy group, a propyloxy group, a butyloxy group, an octyloxy group, adodecyloxy group, a methoxyethoxy group, a phenoxyethoxy group, amethoxycarbonylethyl group, an ethoxycarbonylethyl group, apropyloxycarbonylethyl group, a butyloxycarbonylethyl group, anoctyloxycarbonylethyl group, a phenoxycarbonylethyl group, a phenylgroup, a tolyl group, a chlorine atom, a fluorine atom, a bromine atom,and so on. Bivalent substituents include the groups given below.

[0049] X: —CH₂—, —CH₂—CH₂—, —O—CH₂—CH₂—O—, —OCH₂)₈—O—,

[0050] W: —OCH₂₆O—,

[0051]  —OCH₂₂OCH₂₂O—, —OCH₂₂SCH₂₂O—

[0052] Y:

[0053]  —CH₂CH₂—CO₂—CH₂₄OCO—CH₂—CH₂—,—CH₂—CH₂—CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CO—CH₂—CH₂—,—CH₂—CH₂—OCO(CH₂)₈CO₂—CH₂—CH₂—, —CH₁—CH₂—CONH(CH₂)₆NHCO—CH₂—CH₂—

[0054] Specific examples of the substituents represented by Z include ahydrogen atom, a chlorine atom, a methyl group, an ethyl group, a propylgroup, a hexyl group, a methoxy group, an ethoxy group, a propyloxygroup, and an octyloxy group.

[0055] Specific examples of the monovalent substituents represented by Ainclude a methanesulfonyl group, an ethanesulfonyl group, abutanesulfonyl group, a benzenesulfonyl group, a 4-methylbenzenesulfonylgroup, a 2-mesitylenesulfonyl group, a 4-methoxybenzenesulfonyl group, a4-octyloxybenzenesulfonyl group, a 2,4,6-triisopropylbenzenesulfonylgroup, a β-styrenesulfonyl group, a vinylbenzenesulfonyl group, a4-chlorobenzenesulfonyl group, a 2,5-dichlorobenzenesulfonyl group, a2,4,5-trichlorobenzenesulfonyl group, a 1-naphthalenesulfonyl group, a2-naphthalenesulfonyl group, a quinolinesulfonyl group, athiophenesulfonyl group, an acetyl group, a propionyl group, a butyrylgroup, a pivaloyl group, a lauroyl group, a stearoyl group, a benzoylgroup, a cinnamoyl group, a furoyl group, a nicotinoyl group, amethoxycarbonyl group, an ethoxycarbonyl group, a phenoxycarbonyl group,a hexylaminocarbonyl group, a phenylaminocarbonyl group, adiphenylphosphoryl group, a diethylphosphoryl group, a 2-nitrobenzylgroup, a 3,5-dimethoxybenzyl group, a 3,4,5-trimethoxybenzyl group, atrimethylsilyl group, a triethylsilyl group, a t-butyldimethylsilylgroup, a diethylisopropylsilyl group, a dimethylphenylsilyl group, adiphenylmethylsilyl group, and a triphenylsilyl group. Specific examplesof the bivalent substituents represented by A include the followinggroups.

[0056] —CO—, —COCO—, —COCH₂₈CO—, —SO—, —SO₂—

[0057] In the case where A is —SiR₄R₅R₆, a photoacid generating agentsuch as an ammonium salt, a diazonium salt, an iodonium salt, asulfonium salt, a phosphonium salt, or an onium salt may also be used atthe same time in order to enhance photoreactivity. Details of thespecific examples of these photoacid generating agents are described in“Organic Materials for Imaging” edited by Research Association ofOrganoelectronics Materials, 1993.

[0058] Specific examples (Specific Examples (1) to (49)) of thecompounds represented by the general formulae (1) to (4) are givenbelow, though it should be understood that the present invention is notrestricted to these examples. TABLE 1 In a case where m is 1 in thegeneral formula (1) Speci- fic Ex- amples A X W Y Z (1)

H H CH₃ H (2)

″ ″ C₄H₉(t) ″ (3)

″ ″ C₈H₁₇(t) ″ (4)

″ ″ C₄H₉(t) Cl (5)

″ ″ ″ H (6)

″ ″ ″ ″ (7)

C₄H₉(sec) ″ C₄H₉(t) H (8)

″ ″ ″ ″ (9)

″ ″ ″ ″ (10)

″ ″ ″ ″ (11)

″ ″ ″ ″ (12)

″ ″ ″ ″ (13)

C₄H₉(t) ″ ″ H (14)

″ ″ ″ Cl (15)

″ ″ ″ CH₃

[0059] TABLE 2 In a case where m is 1 in the general formula (1)Specific Examples A X W Y Z (16)

C₅H₁₁(t) H C₅H₁₁(t) H (17)

C₁₂H₂₅ H CH₂ H (18)

H OC₅H₁₇ H H (19)

H H OCH₃ H (20)

C₄H₉(t) H CH₂CH₂CO₂CH₂ H (21)

″ ″ CH₂CH₂CO₂C₂H₅ Cl (22)

″ ″ CH₂CH₂CO₂C₂H₇ ″ (23)

″ ″ CH₂CH₂CO₂C₈H₁₇ ″ (24)

″ ″ CH₃ ″ (25)

CH₂CH═CH₂ ″ C₄H₉(t) H (26)

″ ″ C₄H₉(t) Cl (27)

″ ″ C₈H₁₇(t) H (28) COCH₃ H H C₄H₉(t) ″ (29)

C₄H₉(t) H C₄H₉(t) Cl (30) CO₂CH₃

H

H

[0060] TABLE 3 In a case where m is 1 in the general formula (1)Specific Examples A X W Y Z (31) CO₂C₂H₅ C₄H₉(t) H C₄H₉(t) OCH₃ (32)

C₄H₉(t) H CH₂CH₂CO₂C₃H₁₃ H (33)

C₅H₁₁(t) H C₅H₁₁(t) H (34)

″ ″ ″ ″ (35)

″ ″ ″ ″ (36) PO(OC₂H₅)₂ ″ ″ ″ ″ (37)

″ ″ ″ ″ (38)

″ ″ ″ ″ (39)

″ ″ ″ ″ (40) Si(CH₃)₃ C₄H₉(sec) ″ C₄H₉(t) ″ (41) Si(C₂H₅)₃ ″ ″ ″ ″ (42)Si(CH₃)₂C₄H₉(t) ″ ″ ″ ″ (43)

″ ″ ″ ″ (44)

H H ″ ″ (45) Si(CH₃)₃ C₄H₉(t) H ″ ″

[0061] In a case where m is 2 in the general formula (1)

[0062] When the heat-sensitive recording material is fixed, thecompounds represented by the general formulae (1) to (4) do not absorbthe fixing light. And, these compounds can enhance light stability ofimages by absorbing ultraviolet light having longer wavelengths afterimages are formed.

[0063] In the present invention, the compounds represented by thegeneral formulae (1) to (4) can be easily synthesized by conventionallyknown methods.

[0064] In the present invention, in order to inhibit stain formation dueto a byproduct that is formed when an ultraviolet light absorber isformed after the compounds represented by the general formulae (1) to(4) react due to the effect of light or heat, preferably a compoundrepresented by the following general formula (5) is also used at thesame time. The compound represented by the general formula (5) is aso-called radical trapping agent. If this compound is used, the stainformation can be inhibited.

[0065] General Formula (5)

[0066] In the general formula (5), R_(a) to R_(d) each represents ahydrogen atom, an alkyl group, an alkoxy group, an ester group, an arylgroup, or a halogen atom. Among these substituents, the alkyl group maybe a straight-chain alkyl group or a branched alkyl group. Further, thealkyl group may have an unsaturated bond. Furthermore, the alkyl groupmay bear a substituent such as an alkoxy group, an aryloxy group, analkoxycarbonyl group, an aryl group, a hydroxyl group, or the like.

[0067] Among the substituents represented by R_(a), a hydrogen atom ispreferable. Among the substituents represented by R_(b), a hydrogen atomis preferable. Among the substituents represented by R_(c), a hydrogenatom, an alkyl group, and an aryl group are preferable. Among thesubstituents represented by R_(d). an ester group, an alkyl group, andan aryl group are preferable.

[0068] The compound represented by the general formula (5) may be apolar compound or a nonpolar compound. A nonpolar compound is preferablein view of suitability to encapsulation into microcapsules.

[0069] Specific examples of the compounds represented by the generalformula (5) are given below, though it should be understood that thepresent invention is not restricted to these examples.

[0070] Specific examples of the compounds represented by the generalformula (5) include the following structural formula (A), styrene andpolymeric oligomers thereof, and the following (A-1 to A-107). Amongthese, the structural formula (A) and an α-methylstyrene dimer arepreferable. The structural formula (A) is more preferable from thestandpoint of molecular weight and viscosity.

[0071] In the present invention, the compounds represented by thegeneral formula (5) can be easily synthesized according toconventionally known methods. On the other hand, commercialized productssuch as “1A-A”, “L-A”, and “S-A” manufactured by Kyoei Sha Yushi KagakuCo., Ltd. may be used.

[0072] In the present invention, a compound represented by any of thegeneral formulae (1) to (4) may be incorporated in any of the layersconstituting the heat-sensitive recording material, or alternatively,may be incorporated in an additional layer such as a light and heatcontrolling layer. Preferably, a compound represented by any of thegeneral formulae (1) to (4) is incorporated in a protective layer, whichis disposed above a color-forming layer, from the standpoint ofeffectively utilizing the function of the protective layer as alight-shielding layer. More preferably, a light transmittancecontrolling layer is provided on the heat-sensitive layer side oppositeto the support side and a compound represented by any of the generalformulae (1) to (4) is incorporated in the light transmittancecontrolling layer. In the case where a protective layer is present, thelight transmittance controlling layer is preferable provided between theheat-sensitive layer and the protective layer, in view of, for example,the function as a light-shielding layer of the light transmittancecontrolling layer.

[0073] In the present invention, the coating weight of the compoundrepresented by any of the general formulae (1) to (4) is preferably 0.05g/m² or more and more preferably in the range of 0.1 to 1.5 g/m². If thecoating weight is less than 0.1 g/m², the lightfastness tends to becomeinferior because the control of the transmission of light, particularlythe reduction of the transmittance of the light within an ultravioletrange after irradiation with light whose wavelength is in a rangenecessary for fixing, is difficult to perform. On the other hand, thecoating weight exceeding 1.5 g/m²is disadvantageously excessive.

[0074] The compound represented by any of the general formulae (1) to(4) may be used singly or in a combination of two or more.

[0075] In the present invention, the content of the compound representedby the general formula (5) is preferably about 0.05 to 20 times, morepreferably 0.1 to 5 times, and most preferably 0.3 to 2 times thecontent of the compound represented by any of the general formulae (1)to (4). If the content of the compound represented by the generalformula (5) is less than 0.3 times, the stain inhibiting effect tends todiminish. On the other hand, if the content of the compound representedby the general formula (5) is more than 2 times, the coating weightincreases and the stain inhibiting effect per unit content tends todiminish.

[0076] The compound represented by the general formula (5) may be usedsingly or in a combination of two or more.

[0077] In the present invention, the compound represented by any of thegeneral formulae (1) to (4) and the hydrogen donor are incorporated intothe heat-sensitive recording material according to any of the followingmethods. That is, (1) a method in which the compound and the hydrogendonor are used as a dispersion of solid particles; (2) a method in whichthe compound and the hydrogen donor are used as an emulsifieddispersion; (3) a method in which the compound and the hydrogen donorare used as a polymer dispersion; (4) a method in which the compound andthe hydrogen donor are used as a latex dispersion; and (5) a method inwhich the compound and the hydrogen donor are used after beingencapsulated in microcapsules. Among these methods, (2) a method inwhich the compound and the hydrogen donor are used as an emulsifieddispersion and (5) a method in which the compound and the hydrogen donorare used after being encapsulated in microcapsules are preferable. Fromthe viewpoint of the prevention of the diffusion of the ultravioletlight absorber precursor, (5) a method in which the compound and thehydrogen donor are used after being encapsulated in microcapsules ismore preferable.

[0078] (2) A method in which the compound and the hydrogen donor areused as an emulsified dispersion is as follows. First, the compoundrepresented by any of the general formulae (1) to (4) and the hydrogendonor are dissolved in an oil. The oil may be a solid, a liquid, or apolymer at normal temperatures. Examples of the oil include low-boilingauxiliary solvents such as acetic ester, methylene chloride, andcyclohexanone and/or phosphoric ester, phthalic ester, acrylic ester,methacrylic ester, other carboxylic acid esters, fatty acid amides,alkylated biphenyl, alkylated terphenyl, alkylated naphthalene, diarylethane, chlorinated paraffin, alcohols, phenols, ethers, monoolefins,and epoxies. Specific examples include high-boiling oils such astricresyl phosphate, trioctyl phosphate, octyldiphenyl phosphate,tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurylphthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycolbenzoate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trioctyltrimellitate, acetyltriethyl citrate, octyl maleate, dibutyl maleate,isoamylbiphenyl, chlorinated paraffin, diisopropylnaphthalene,1,1′-ditolylethane, 2,4-di-t-amylphenol,N,N-dibutyl-2-butoxy-5-t-octylaniline, 2-ethylhexyl hydroxybenzoate, andpolyethylene glycol. Among these high-boiling oils, alcohols, phosphoricesters, carboxylic acid esters, alkylated biphenyl, alkylated terphenyl,alkylated naphthalene, and diaryl ethane are preferable. Further, acarbonization inhibitor such as a hindered phenol or a hindered aminemay be added to these high-boiling oils. In particular, an oilcomprising an unsaturated fatty acid is preferable as the oil andexamples thereof include an α-methylstyrene dimer. Examples of theα-methylstyrene dimer include MSD100 (trade name, manufactured by MitsuiToatsu Chemicals, Inc.).

[0079] An oil solution containing the compound represented by any of thegeneral formulae (1) to (4) and the hydrogen donor is added into anaqueous solution of a water-soluble polymer, and the mixture issubjected to emulsifying dispersion by means of a colloid mill,homogenizer, or ultrasonic wave. A water-soluble polymer such aspolyvinyl alcohol is used as the water-soluble polymer in theabove-mentioned process. In this case, a hydrophobic polymer emulsion orlatex or the like can be used together with polyvinyl alcohol. Examplesof the water-soluble polymer include polyvinyl alcohol, silanol-modifiedpolyvinyl alcohol, carboxy-modified polyvinyl alcohol, amino-modifiedpolyvinyl alcohol, itaconic acid-modified polyvinyl alcohol,styrene/maleic anhydride copolymers, butadiene/maleic anhydridecopolymers, ethylene/maleic anhydride copolymers, isobutylene/maleicanhydride copolymers, polyacrylamide, polystyrenesulfonic acid,polyvinyl pyrrolidone, ethylene/acrylic acid copolymers, and gelatin.Among these water-soluble polymers, carboxy-modified polyvinyl alcoholis particularly preferable. Examples of the hydrophobic polymer emulsionor latex include styrene/butadiene copolymers, carboxy-modifiedstyrene/butadiene copolymers, and acrylonitrile/butadiene copolymers. Inthis case, a conventionally known surfactant or the like may be added asnecessary.

[0080] (5) As for the method of encapsulation in microcapsules, aconventionally known method of encapsulation in microcapsules can beemployed. The method is as follows. The compound represented by any ofthe general formulae (1) to (4), the hydrogen donor, and a microcapsulewall precursor are dissolved in an organic solvent which is difficultlysoluble or insoluble in water. The resulting solution is added into anaqueous solution of a water-soluble polymer; subjected to emulsifyingdispersion by means of a homogenizer or the like; and heated so that awall film of a polymeric substance constituting a microcapsule wall filmis formed in the oil/water interface. Specific examples of the polymericmaterial constituting a microcapsule wall film include a polyurethaneresin, a polyurea resin, a polyamide resin, a polyester resin, apolycarbonate resin, an aminoaldehyde resin, a melamine resin, apolystyrene resin, a styrene/acrylate copolymer resin, astyrene/methacrylate copolymer resin, gelatin, and polyvinyl alcohol.Among these examples, microcapsules having a wall film composed of apolyurethane and/or polyurea resin are particularly preferable.

[0081] The microcapsules having a wall film composed of a polyurethaneand/or polyurea resin are prepared by the steps of blending amicrocapsule wall precursor such as a polyvalent isocyanate into a corematerial to be encapsulated, subjecting the blend to emulsifyingdispersion into an aqueous solution of a water-soluble polymer such aspolyvinyl alcohol, and heating the resulting solution so that a polymerforming reaction takes place in the interface of oil droplets.

[0082] Some specific examples of the polyvalent isocyanate compoundinclude diisocyanates such as m-phenylene diisocyanate, p-phenylenediisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate,naphthalene-1,4-diisocyanate, diphenylmethane-4,4′-diisocyanate,3,3′-diphenylmethane-4,4′-diisocyanate, xylylene-1,4-diisocyanate,4,4′-diphenylpropane diisocyanate, trimethylene diisocyanate,hexamethylene diisocyanate, propylene-1,2-diisocyanate,butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate,cyclohexylene-1,4-diisocyanate, 3,3′-dimethoxy-biphenyl diisocyanate,xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate,2-methylxylylene-1,3-diisocyanate, cyclohexylene-1,3-diisocyanate,1,4-bis(isocyanatomethyl)cyclohexane, and1,3-bis(isocyanatomethyl)cyclohexane; triisocyanates such as4,4′,4″-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate;tetraisocyanates such as4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate; and isocyanateprepolymers such as a hexamethylene diisocyanate/trimethylol propaneadduct, a 2,4-tolylene diisocyanate/trimethylol propane adduct, axylylene diisocyanate/trimethylol propane adduct, and a tolylenediisocyanate/hexanetriol adduct. If necessary, two or more kinds of thepolyvalent isocyanate compounds can be used. Among these polyvalentisocyanate compounds, a compound having three or more isocyanate groupsin the molecule is particularly preferable.

[0083] In the method of encapsulation, as for the organic solvents fordissolving the compound represented by any of the general formulae (1)to (4) and the hydrogen donor, the oils illustrated for use in theemulsifying dispersion can be used. Specific examples of the organicsolvent include tricresyl phosphate, trioctyl phosphate,dioctylphthalate, dioctyl sebacate, dioctyl adipate, dibutyl maleate,and O-methylstyrene dimer.

[0084] Examples of the water-soluble polymer include polyvinyl alcohol,modified polyvinyl alcohol, methyl cellulose, sodiumpolystyrenesulfonate, styrene/maleic acid copolymers, gelatin or gelatinderivatives, and polyethylene glycol or polyethylene glycol derivatives.

[0085] The particle diameter of the microcapsule is preferably 0.05 to1.0 μm and more preferably 0.1 to 0.7 μm.

[0086] In the method of encapsulation into microcapsules, either thecompound represented by any of the general formulae (1) to (4) or thehydrogen donor may be encapsulated or both of the compound representedby any of the general formulae (1) to (4) and the hydrogen donor may beencapsulated. Preferably, both of the compound represented by any of thegeneral formulae (1) to (4) and the hydrogen donor are encapsulated.More preferably, both of the compound represented by any of the generalformulae (1) to (4) and the hydrogen donor are enclosed in the samecapsule.

[0087] In the present invention, in order to lessen the coloration dueto browning by light, a compound known as a reducing agent can be usedtogether with the compound represented by any of the general formulae(1) to (4) and the hydrogen donor. Although the reducing agent may bepresent inside or outside the microcapsule, the reducing agent ispreferably present inside the microcapsule. In the case where thereducing agent is present outside the microcapsule, a compound, whichpenetrates into the microcapsule at the time of heat printing, is usedas the reducing agent. Examples of the reducing agent includehydroquinone compounds, hydrazide compounds, hydroxy compounds,phenidone compounds, catechol compounds, resorcinol compounds,hydroxyhydroquinone compounds, pyrrologlycinol compounds, phenolcompounds, phenylhydrazide compounds, gallic acid compounds, ascorbicacid compounds, and ethylene glycol compounds. These are described inJP-A Nos.3-191341, 3-25434, 1-252953,2-302753, 1-129247, 1-227145,1-243048, 2-262649, etc. Specific examples thereof includeN-phenylacetohydrazide, N-phenylbutylylhydrazide, p-t-butylphenol,2-azidebenzoxazole, and the following compounds.

[0088] In the present invention, the heat-sensitive recording materialpreferably comprises a support, a photo-fixing type heat-sensitiverecording layer, and optional layers such as an interlayer and aprotective layer, each provided on the support. It is also possible toprovide another layer containing a compound described in JP-ANos.7-276808, 9-1928, 9-39395, 9-39396, 9-95487, 9-301958, 11-291629,6-191155, and 12-206644.

[0089] In the present invention, preferably the heat-sensitive recordingmaterial has a photo-fixing type heat-sensitive recording layercontaining a diazonium salt compound whose maximum absorption wavelengthis 365±40 nm and a coupler which reacts with the diazonium salt compoundto develop a color and a photo-fixing type heat-sensitive recordinglayer containing a diazonium salt compound whose maximum absorptionwavelength is 425±40 nm and a coupler which reacts with the diazoniumsalt compound to develop a color.

[0090] The present invention may also be a heat-sensitive recordingmaterial comprising a support having disposed thereon a photo-fixingtype heat-sensitive recording layer containing a diazonium salt compoundwhose maximum absorption wavelength is 425±40 nm and a coupler whichreacts with the diazonium salt compound to develop a color and aphoto-fixing type heat-sensitive recording layer containing a diazoniumsalt compound whose maximum absorption wavelength is 365±40 nm and acoupler which reacts with the diazonium salt compound to develop acolor, in the order listed.

[0091] Further, the present invention may also be a heat-sensitiverecording material having a photo-fixing type heat-sensitive recordinglayer containing a diazonium salt compound whose maximum absorptionwavelength is less than 380 nm and a coupler which reacts with thediazonium salt compound to develop a color and a photo-fixing typeheat-sensitive recording layer containing a diazonium salt compoundwhose maximum absorption wavelength is more than 390 nm and a couplerwhich reacts with the diazonium salt compound to develop a color.

[0092] If a plurality of photo-fixing type heat-sensitive recordinglayers are present, a multicolor heat-sensitive recording material canbe obtained by causing the photo-fixing type heat-sensitive recordinglayers to develop different colors. That is, full-color image recordingis possible by selecting the colors to be developed by the photo-fixingtype heat-sensitive recording layers such that these colors constitutethe three primary colors for subtractive color mixing, i.e., yellow,magenta, and cyan, respectively. In this case, the color developingmechanism of the photo-fixing type heat-sensitive recording layer (thelowermost layer of the photo-fixing type heat-sensitive recordinglayers) in direct contact with the support is not limited to thecombination of an electron-donating dye and an electron-accepting dye.Accordingly, the combination may be, for example, any of the followingsystems, i.e., a diazo coloration system consisting of a diazonium saltand a coupler which undergoes a color-forming reaction with thediazonium salt; a base-coloration system in which contact with a basiccompound develops a color; a color-forming system by chelating; and acolor-forming system in which an elimination reaction with anucleophilic agent causes color formation. It is preferable to provide,on this photo-fixing type heat-sensitive recording layer, two or morephoto-fixing type heat-sensitive recording layers each containing adiazonium salt compound having a different maximum absorption wavelengthand a coupler which reacts with the diazonium salt compound to develop acolor and to superpose on the layers, a layer (light-transmittancecontrolling layer) containing the compound represented by any of thegeneral formulae (1) to (4) and a protective layer, in the order listed.

[0093] The color-forming components to be used in the photo-fixing typeheat-sensitive recording layers in the present invention may beconventionally known ones. Particularly preferable are the color-formingcomponents utilizing the reaction between a diazonium salt compound anda coupler, and the color-forming components utilizing the reactionbetween an electron-donating colorless dye and an electron-acceptingcompound. Examples of the compounds which are used in the photo-fixingtype heat-sensitive recording layer containing a diazonium salt compoundand a coupler which reacts with the diazonium salt compound to develop acolor when heated, include a diazonium salt compound, a coupler capableof reacting with the diazonium salt to develop a color, and a basiccompound which accelerates the reaction between the diazonium saltcompound and the coupler. Details of the diazonium salt compound,coupler, and base are described in, for example, JP-B Nos.4-75147,6-55546, and 6-79867, JP-A Nos.4-201483, 60-49991, 60-242094, 61-5983,63-87125, 4-59287, 5-185717,7-88356, 7-96671, 8-324129, 9-38389,5-185736, 5-8544, 59-190866, 62-55190, 60-6493, 60-259492, 63-318546,4-65291, 5-204089, 8-310133, 8-324129, 9-156229, and 9-175017. Specificexamples of the compounds are given below, though it should beunderstood that the present invention is not restricted to theseexamples.

[0094] (Specific Examples of the Diazonium Salt Compound)

[0095] (Specific Examples of the Coupler)

[0096] (Specific Examples of the Base)

[0097] The base may be used singly or in a combination of two or more.Examples of the base include nitrogen-containing compounds such astertiary amines, piperizines, piperazines, amidines, formamidines,pyridines, guanidines, and morpholines.

[0098] Among these compounds, particularly preferred are piperazinessuch as N,N′-bis(3-phenoxy-2-hydroxypropyl)piperazine,N,N′-bis(3-(p-methylphenoxy)-2-hydroxypropyl)piperazine,N,N′-bis(3-(p-methoxyphenoxy)-2-hydroxypropyl)piperazine,N,N′-bis(3-phenylthio-2-hydroxypropyl)piperazine,N,N′-bis(3-(β-naphthoxy)-2-hydroxypropyl)piperazine,N-3-(β-naphthoxy)-2-hydroxypropyl-N′-methylpiperazine, and1,4-bis((3-(N-methylpiperazino)-2-hydroxy)propyloxy)benzene; morpholinessuch as N-(3-(β-naphthoxy)-2-hydroxy)propylmorpholine,1,4-bis((3-morpholino-2-hydroxy)propyploxy)benzene, and1,3-bis((3-morpholino-2-hydroxy)propyploxy)benzene; piperidines such asN-(3-phenoxy-2-hydroxypropyl)piperidine and N-dodecylpiperidine; andguanidines such as triphenylguanidines, tricyclohexylguanidines, anddicyclohexylphenylguanidines.

[0099] Details of the electron-donating colorless dye, theelectron-accepting compound, and others are described in JP-ANos.6-328860, 7-290826, 7-314904, 8-324116, 3-37727, 9-31345, 9-111136,9-118073, 11-157221, etc. Specific examples are given below, though itshould be understood that the present invention is not restricted tothese examples.

[0100] (Specific Examples of the Electron-Donating Colorless Dye) TABLE4

R¹ R² R³ i-1 —CH₃ —CH₃ —C₂H₅ i-2 —C₂H₅ —CH₃ —C₂H₅ i-3 —CH(CH₃)₂ —CH₃—C₂H₅ i-4 —C(CH₃)₃ —CH₃ —C₂H₅ i-5

—CH₃ —C₂H₅ i-6

—CH₃ —C₂H₅ i-7 —CH₂OCH₃ —CH₃ —C₂H₅ i-8 —CH₂Cl —CH₃ —C₂H₅ i-9 —CCl₃ —CH₃—C₂H₅ i-10 —CF₃ —CH₃ —C₂H₅ i-11

—CH₃ —C₂H₅ i-12

—CH₃ —C₂H₅ i-13 —C₃H₇(n) —CH₃ —C₂H₅ i-14 —CH₃ —CH₃ —C₄H₉(n) i-15 —CH₃—CH₃ —C₈H₁₇(n) i-16 —CH(CH₃)₂ —CH₃ —C₄H₉(n) i-17

—CH₃ —C₅H₁₁(n) i-18 —CH₂OCH₃ —CH₃ —C₈H₁₇(n)

[0101] TABLE 5

R¹ R² R³ i-19 —CH₃ —CH₃

i-20

—CH₃ —C₆H₁₃(n) i-21 —CH₃

—C₂H₅ i-22 —CH₃

—C₈H₁₇(n) ia-1 —C₅H₁₁(n) —CH₃ —C₂H₅ ia-2 —C₇H₁₅(n) —CH₃ —C₂H₅ ia-3—C₁₇H₃₅(n) —CH₃ —C₂H₅ ia-4

—CH₃ —C₂H₅ ia-5

—CH₃ —C₂H₅ ia-6

—CH₃ —C₂H₅ ia-7 —CH₃ —CH₃ —C₅H₁₁(n) ia-8 —CH₃ —CH₃ —CH(CH₃)₂ ia-9—C₃H₇(n) —CH₃ —C₈H₁₇(n) ia-10 —C₄H₉(n) —CH₃ —C₈H₁₇(n)

[0102] TABLE 6

R¹ R² R³ ia-11 —CH(CH₃)₂ —CH₃ —C₈H₁₇(n) ia-12 —C₃H₇(t) —CH₃ —C₈H₁₇(n)ia-13 —C₄H₉(t) —CH₃ —C₈H₁₇(n) ia-14

—CH₃ —C₈H₁₇(n) ia-15

—CH₃ —C₈H₁₇(n) ia-16

—CH₃ —C₈H₁₇(n) ia-17 —C₃H₇(n) —CH₃

ia-18 —CH₃ —CH₃

[0103]

[0104] (Specific Examples of the Electron-Accepting Compound)

[0105] Examples of the electron-accepting compound include phenolderivatives, salicylic acid derivatives, hydroxybenzoates, etc. Inparticular, bisphenols and hydroxybenzoates are preferable. Somespecific examples thereof include 2,2-bis(p-hydroxyphenyl)propane (i.e.,bisphenol A),4,4′-(p-phenylenediisopropylidene)diphenol (i.e., bisphenolP), 2,2-bis(p-hydroxyphenyl)pentane, 2,2-bis(p-hydroxyphenyl)ethane,2,2-bis(p-hydroxyphenyl)butane,2,2-bis(4′-hydroxy-3′,5′-dichlorophenyl)propane,1,1-(p-hydroxyphenyl)cyclohexane, 1,1-(p-hydroxyphenyl)propane,1,1-(p-hydroxyphenyl)pentane, 1,1-(p-hydroxyphenyl)-2-ethylhexane,3,5-di(α-methylbenzyl)salicylic acid and polyvalent metal salts thereof,3,5-di(t-butyl)salicylic acid and polyvalent metal salts thereof,3-α,α-dimethylbenzylsalicylic acid and polyvalent metal salts thereof,butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexylp-hydroxybenzoate, p-phenylphenol, and p-cumylphenol.

[0106] In the present invention, the methods of using the diazonium saltcompound, the coupler which reacts with the diazonium salt compound todevelop a color when heated, the basic material, the electron-donatingcolorless dye, the electron-accepting compound, and the sensitizer arenot particularly limited. Examples of these methods include (1) a methodin which these compounds are used as a dispersion of solid particles;(2) a method in which these compounds are used as an emulsifieddispersion; (3) a method in which these compound are used as a polymerdispersion; (4) a method in which these compounds are used as a latexdispersion; and (5) a method in which these compounds are used afterbeing encapsulated in microcapsules. Among these methods, from theviewpoint of storability, a method in which these compounds are usedafter being encapsulated in microcapsules is more preferable. Inparticular, it is preferable to enclose the diazonium salt compound inmicrocapsules in a color-forming system utilizing the reaction betweenthe diazonium salt compound and the coupler; and it is preferable toenclose the electron-donating colorless dye in microcapsules in acolor-forming system utilizing the reaction between theelectron-donating colorless dye and the electron-accepting compound.

[0107] In the present invention, a plurality of the photo-fixing typeheat-sensitive recording layers may be laminated. A multicolorheat-sensitive recording material can be obtained by changing the colorsof the constituent photo-fixing type heat-sensitive recording layers.Although the layer construction is not particularly limited, preferableis a multicolor heat-sensitive recording material manufactured bylaminating two photo-fixing type heat-sensitive recording layers, withthe two heat-sensitive recording layers respectively comprising twodifferent diazonium salt compounds sensitive to respectively differentwavelengths and couplers which reacts with the diazonium salt compoundsto develop a different color when heated, and a photo-fixing typeheat-sensitive recording layer which comprises a combination of anelectron-donating colorless dye and an electron-accepting compound. Thatis, the multicolor heat-sensitive recording material comprise a supporthaving disposed thereon a first photo-fixing type heat-sensitiverecording layer containing an electron-donating colorless dye and aelectron-accepting compound, a second photo-fixing type heat-sensitiverecording layer containing a diazonium salt compound whose maximumabsorption wavelength is 365±40 nm and a coupler which reacts with thediazonium salt compound to develop a color when heated, and a thirdphoto-fixing type heat-sensitive recording layer containing a diazoniumsalt compound whose maximum absorption wavelength is 425±40 nm and acoupler which reacts with the diazonium salt compound to develop a colorwhen heated. In the above-described example, full-color image recordingis possible if the colors to be developed in the photo-fixing typeheat-sensitive recording layers are selected such that these colorsconstitute the three primary colors, i.e., yellow, magenta, and cyan,respectively, in the subtractive color mixing.

[0108] The method of recording in this multicolor heat-sensitiverecording material is as follows. First, the third photo-fixing typeheat-sensitive recording layer is heated so that a color is formed bythe reaction between the diazonium salt compound and the couplercontained in the layer. Next, the third photo-fixing type heat-sensitiverecording layer is irradiated with light having a wavelength of 425±40nm so that the diazonium salt compound remaining unreacted in the thirdphoto-fixing type heat-sensitive recording layer is decomposed. Afterthat, heat in an amount to cause the second photo-fixing typeheat-sensitive recording layer to develop a color is applied to thesecond photo-fixing type heat-sensitive recording layer so that a coloris formed by the reaction between the diazonium salt compound and thecoupler contained in the second layer. When the heat is applied,although the third photo-fixing type heat-sensitive recording layer isalso heated strongly, the third photo-fixing type heat-sensitiverecording layer does not develop any color because the diazonium saltcompound is already decomposed to an extent that its color-formingcapability is lost. Further, the second photo-fixing type heat-sensitiverecording layer is irradiated with light having a wavelength of 365±40nm so that the diazonium salt compound remaining unreacted in the secondphoto-fixing type heat-sensitive recording layer is decomposed. beFinally, heat in an amount to cause the first photo-fixing typeheat-sensitive recording layer to develop a color is applied to thefirst photo-fixing type heat-sensitive recording layer. When the heat isapplied, although the third and second photo-fixing type heat-sensitiverecording layers are also heated strongly, these photo-fixing typeheat-sensitive recording layers do not develop any color because thediazonium salt compounds are already decomposed to an extent that theircolor-forming capability is lost.

[0109] In the present invention, in order to further improve thelightfastness, conventionally known antioxidants as described in thefollowing publications can be used. For example, EP 310551A, GermanPatent Application Laid-Open (OLS) No. 3435443, EP 310552A, JP-ANo.3-121449, EP 459416A, JP-A Nos.2-262654, 2-71262, and 63-163351, U.S.Pat. No. 4,814,262, JP-A Nos.54-48535, 5-61166, and 5-119449, U.S. Pat.No. 4,980,275, JP-A Nos.63-113536 and 62-262047, EP 223739A, EP 309402A,EP 309401A, etc.

[0110] It is also effective to use additives which are conventionallyknown in heat-sensitive recording materials and pressure-sensitiverecording materials. Some examples of these antioxidants include thecompounds described in JP-A Nos.60-125470, 60-125471, 60-125472,60-287485, 60-287486, 60-287487, 62-146680, 60-287488, 62-282885,63-89877, 63-88380, 63-088381, 01-239282, 04-291685, 04-291684,05-188687, 05-188686, 05-110490, 05-1108437, 05-170361, 63-203372,63-224989, 63-267594, 63-182484, 60-107384, 60-107383, 61-160287,61-185483, 61-211079, 63-251282, and 63-051174, JP-B Nos. 48-043294 and48-033212, etc.

[0111] A conventionally known binder can be used as the binder in thepresent invention. Examples of the binder include water-soluble polymerssuch as polyvinyl alcohol and gelatin, and polymer latices, etc.

[0112] A plastic film, paper, plastic resin-laminated paper, syntheticpaper, or the like can be used as the support in the present invention.

[0113] In the present invention, in the case where heat-sensitivecolor-forming layers for different colors are laminated, an interlayercan be provided in order to prevent color mixing, etc. In theinterlayer, a water-soluble polymeric compound is used. Examples of thewater-soluble polymeric compound include polyvinyl alcohol, modifiedpolyvinyl alcohol, methyl cellulose, sodium polystyrenesulfonate,styrene/maleic acid copolymers, and gelatin.

[0114] The light transmittance controlling layer and the protectivelayer in the present invention may contain various pigments, a releaseagent, and the like besides the water-soluble polymeric compound similarto that for the interlayer.

EXAMPLES

[0115] The present invention is described using the following examples.However the invention is not limited by these examples. All “parts” and“percentages” are by weight unless otherwise specified.

Example 1

[0116] <Preparation of a Phthalated Gelatin Solution>

[0117] A mixture composed of 32 parts of phthalated gelatin (trade name:MGP Gelatin, manufactured by Nitsubi Kolegen Co., Ltd.), 0.9143 parts of1,2-benzothiazoline-3-one (a 3.5% methanol solution, manufactured byDaitoh Kagaku Kogyosho Co., Ltd.), and 367.1 parts of ion-exchangedwater was made into a solution at 40° C. to thereby prepare an aqueoussolution of phthalated gelatin.

[0118] <Preparation of a Gelatin Solution for Making an Emulsion>

[0119] A mixture composed of 25.5 parts of alkali-treated low-iongelatin (trade name: No.750 Gelatin, manufactured by Nitta Gelatin, Co.,Ltd.), 0.7286 parts of 1,2-benzothiazoline-3-one (a 3.5% methanolsolution, manufactured by Daitoh Kagaku Kogyosho Co., Ltd.), 0.153 partsof calcium hydroxide, and 143.6 parts of ion-exchanged water was madeinto a solution at 50° C. to thereby prepare an aqueous solution ofgelatin for making an emulsion.

[0120] (1) Preparation of a Coating Solution (a) for YellowHeat-Sensitive Recording Layer

[0121] <Preparation of a Solution (a) having Microcapsules EnclosingDiazonium Salt Compounds>

[0122] To 16.1 parts of ethyl acetate were added 2.2 parts of thefollowing diazonium salt compound (A) (maximum absorption wavelength:420 nm), 2.2 parts of the following diazonium salt compound (B) (maximumabsorption wavelength: 420 nm), 4.8 parts of monoisopropylbiphenyl, 4.8parts of diphenyl phthalate, and 0.4 parts ofdiphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide (trade name: LUCILINTPO, manufactured by BASF Japan Co., Ltd.) The mixture was heated to 40°C. and made into a homogeneous solution. To the solution thus obtainedwas added 8.6 parts of a mixture composed of a xylylenediisocyanate/trimethylol propane adduct and a xylylenediisocyanate/bisphenol A adduct (trade name: TAKENATE D-119N (a 50%ethyl acetate solution), manufactured by Takeda Chemical Industries,Ltd.) as a capsule wall forming material, and the resulting mixture wasuniformly stirred. In this way, a blend solution (I) was obtained.

[0123] A blend solution (II) was obtained by adding 16.3 parts ofion-exchanged water and 0.34 parts of Scraph AG-8 (50%) (manufactured byNippon Seika Co., Ltd.) to 58.6 parts of the phthalated gelatin solutiondescribed above.

[0124] The blend solution (I) was added to the blend solution (II) andthe resulting mixture was subjected to emulsifying dispersion by using ahomogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 40°C. Then, 20 parts of water was added to the emulsified solution and thesolution was homogenized. Next, an encapsulation reaction was carriedout by stirring the solution at 40° C. for 3 hours while removing theethyl acetate. After that, 4.1 parts of AMBERLITE IRA68 (manufactured byOrugano Co., Ltd.) and 8.2 parts of AMBERLITE IRC50 (manufactured byOrugano Co., Ltd.) were added as ion-exchange resins and the solutionwas stirred for another hour. The ion-exchange resins were theneliminated by filtration and the concentration of the capsule solutionwas adjusted so that the concentration of the solid components became20.0%. In this way, a solution (a) containing microcapsules enclosingdiazonium salt compounds was obtained. The median particle diameter ofthe microcapsules obtained was found to be 0.36 μm as a result ofmeasurement (by means of LA-700, manufactured by Horiba Seisakusho Co.,Ltd.).

[0125] <Preparation of an Emulsion Solution (a) of a Coupler Compound>

[0126] A blend solution (III) was prepared by dissolving 9.9 parts ofthe following coupler compound (C), 9.9 parts of triphenylguanidine(manufactured by Hodogaya Chemical Company Ltd.), 10.4 parts of4,4′-(m-phenylenediisopropylidene)diphenol (trade name: Bisphenol M,manufactured by Mitsui Petrochemical Co., Ltd.), 3.3 parts of3,3,3′,3′-tetramethyl-5,5′,6,6′-tetra(1-propyloxy)-1,1′-spirobisindan,13.6 parts of 4-(2-ethylhexyloxy)benzenesulfonic acid amide(manufactured by Manac Inc.), 6.8 parts of 4-n-pentyloxybenzenesulfonicacid amide (manufactured by Manac Inc.), and 4.2 parts of calciumdodecylbenzenesulfonate (trade name: PIONIN A-41-C, a 70% methanolsolution, manufacture by Takemoto Oil & Fat Co., Ltd.) in 33.0 parts ofethyl acetate.

[0127] A blend solution (IV) was prepared by blending 206.3 parts of theaqueous solution of alkali-treated gelatin described above with 107.3parts of ion-exchanged water.

[0128] The blend solution (III) was added to the blend solution (IV) andthe resulting mixture was subjected to emulsifying dispersion by using ahomogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 40°C. The emulsion of the coupler compound thus obtained was heated under areduced pressure to remove the ethyl acetate. After that, theconcentration of the emulsion was adjusted so that the concentration ofthe solid components became 26.5%. The median particle diameter of theparticles in the emulsion of the coupler compound obtained was found tobe 0.21 μm as a result of measurement (by means of LA-700, manufacturedby Horiba Seisakusho Co., Ltd.).

[0129] Further, 9 parts of an SBR latex (trade name: SN-307, content ofsolid components: 48%, manufactured by Sumika ABS Latex Co., Ltd.) whoseconcentration had been adjusted to 26.5% was added to 100 parts of theemulsion of the coupler compound and the resulting mixture washomogenized by stirring. In this way, an emulsion solution (a) of acoupler compound was obtained.

[0130] <Preparation of a Coating Solution (a)>

[0131] The solution (a) containing microcapsules enclosing the diazoniumsalt compounds and the emulsion solution (a) of the coupler compoundwere mixed together such that weight ratio of the enclosed couplercompound/diazo compounds became 2.2/1. In this way, a coating solution(a) for yellow heat-sensitive recording layer was obtained.

[0132] (2) Preparation of a Coating Solution (b) for MagentaHeat-Sensitive Recording Layer

[0133] <Preparation of a Solution (b) Containing Microcapsules Enclosinga Diazonium Salt Compound>

[0134] To 15.1 parts of ethyl acetate were added 2.8 parts of thefollowing diazonium salt compound (D) (maximum absorption wavelength:365 nm), 1.9 parts of diphenyl phthalate, 3.9 parts of phenyl2-benzoyloxybenzoate, 4.2 parts of the following compound (E) (LIGHTESTER TMP, manufactured by Kyoei Yushi Kagaku Co., Ltd.), and 0.1 partsof calcium dodecylbenzenesulfonate (trade name: PIONIN A-41-C, a 70%methanol solution, manufacture by Takemoto Oil & Fat Co., Ltd.) and theresulting mixture was made into a homogeneous solution by heating. Tothe solution thus obtained were added 2.5 parts of a mixture composed ofa xylylene diisocyanate/trimethylol propane adduct and a xylylenediisocyanate/bisphenol A adduct (trade name: TAKENATE D-119N (a 50%ethyl acetate solution), manufactured by Takeda Chemical Industries,Ltd.) and 6.8 parts of a xylylene diisocyanate/trimethylolpropane adduct(trade name: TAKENATE D-110N (a 75% ethyl acetate solution),manufactured by Takeda Chemical Industries, Ltd.) as capsule wallforming materials, and the resulting mixture was uniformly stirred. Inthis way, a blend solution (V) was obtained.

[0135] A blend solution (VI) was obtained by adding 21.0 parts ofion-exchanged water to 55.3 parts of the phthalated gelatin solution.

[0136] The blend solution (V) was added to the blend solution (VI) andthe resulting mixture was subjected to emulsifying dispersion by using ahomogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 40°C. Then, 24 parts of water was added to the emulsified solution and thesolution was homogenized. Next, an encapsulation reaction was carriedout by stirring the solution at 40° C. for 3 hours while removing theethyl acetate. After that, 4.1 parts of AMBERLITE IRA68 (manufactured byOrugano Co., Ltd.) and 8.2 parts of AMBERLITE IRC50 (manufactured byOrugano Co., Ltd.) as ion-exchange resins were added and the solutionwas stirred for another hour. The ion-exchange resins were theneliminated by filtration and the concentration of the capsule solutionwas adjusted so that the concentration of the solid components became20.0%. In this way, a solution (b) containing microcapsules enclosing adiazonium salt compound was obtained. The median particle diameter ofthe microcapsules obtained was found to be 0.43 μm as a result ofmeasurement (by means of LA-700, manufactured by Horiba Seisakusho Co.,Ltd.). Diazonium salt compound (D)

[0137] <Preparation of an Emulsion Solution (b) of a Coupler Compound>

[0138] A blend solution (VII) was prepared by dissolving 11.9 parts ofthe following coupler compound (F), 14.0 parts of triphenylguanidine(manufactured by Hodogaya Chemical Company Ltd.), 14.0 parts of4,4′-(m-phenylenediisopropylidene)diphenol (trade name: Bisphenol M,manufactured by Mitsui Petrochemical Co., Ltd.), 14.0 parts of1,1-(p-hydroxyphenyl)-2-ethylhexane, 3.5 parts of3,3,3′,3′-tetramethyl-5,5′,6,6′-tetra(1-propyloxy)-1,1′-spirobisindan,3.5 parts of the following compound (G), 1.7 parts of tricresylphosphate, 0.8 parts of diethyl maleate, and 4.5 parts of calciumdodecylbenzenesulfonate (trade name: PIONIN A-41-C, a 70% methanolsolution, manufacture by Takemoto Oil & Fat Co., Ltd.) in 36.9 parts ofethyl acetate.

[0139] A blend solution (VIII) was prepared by blending 206.3 parts ofthe aqueous solution of alkali-treated gelatin with 107.3 parts ofion-exchanged water.

[0140] The blend solution (VII) was added to the blend solution (VIII)and the mixture was subjected to emulsifying dispersion by using ahomogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 40°C. The emulsion of the coupler compound thus obtained was heated under areduced pressure to remove the ethyl acetate. After that, theconcentration of the emulsion was adjusted so that the concentration ofthe solid components became 24.5%. In this way, an emulsion solution (b)of a coupler compound was obtained. The median particle diameter of theparticles in the emulsion solution of the coupler compound obtained wasfound to be 0.22 μm as a result of measurement (by means of LA-700,manufactured by Horiba Seisakusho Co., Ltd.).

[0141] <Preparation of a Coating Solution (b)>

[0142] The solution (b) containing microcapsules enclosing a diazoniumsalt compound and the emulsion solution (b) of a coupler compound weremixed together such that weight ratio of the enclosed couplercompound/diazo compound became 3.5/1. Further, an aqueous (5%) solutionof polystyrenesulfonic acid (partially neutralized by potassiumhydroxide) in a proportion of 0.2 parts per 10 parts of the solutioncontaining microcapsules was mixed into the solution containingmicrocapsules. In this way, a coating solution (b) for magentaheat-sensitive recording layer was obtained.

[0143] (3) Preparation of a Coating Solution (c) for Cyan Heat-SensitiveRecording Layer

[0144] <Preparation of a Solution (c) Containing Microcapsules Enclosingan Electron-Donating Dye Precursor>

[0145] To 18.1 parts of ethyl acetate were added 7.6 parts of thefollowing electron-donating dye (H), 8.0 parts of a solution composed ofthe mixture of 1-methylpropylphenyl-phenylmethane and1-(1-methylpropylphenyl) -2-phenylethane (trade name: HISOL SAS-310,manufactured by Nippon Petroleum Co., Ltd.), and 8.0 parts of thefollowing compound (I) (trade name: Irgaperm 2140, manufactured byCiba-Geigy Corp.). The mixture was heated and made into a homogeneoussolution.

[0146] To the solution thus obtained was added 7.2 parts of a xylylenediisocyanate/trimethylol propane adduct (trade name: TAKENATE D-110N (a75% ethyl acetate solution), manufactured by Takeda Chemical Industries,Ltd.) and 10.6 parts of polymethylenepolyphenyl polyisocyanate (tradename: MILLIONATE MR-200, manufactured Nippon Polyurethane Industry Co.,Ltd.) as capsule wall forming materials, and the mixture was uniformlystirred. In this way, a blend solution (IX) was obtained.

[0147] A blend solution (X) was obtained by adding 9.5 parts ofion-exchanged water, 0.17 parts of Scraph AG-8 (50%) (manufactured byNippon Seika Co., Ltd.), and 4.3 parts of sodium dodecylbenzenesulfonate(10% aqueous solution) to 28.8 parts of the phthalated gelatin solutiondescribed above.

[0148] The blend solution (IX) was added to the blend solution (X) andthe resulting mixture was subjected to emulsifying dispersion by using ahomogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 40°C. Then, 50 parts of water and 0.12 parts of tetraethylenepentamine wereadded to the emulsified solution thus obtained and the solution washomogenized. Next, an encapsulation reaction was carried out by stirringthe solution at 65° C. for 3 hours while removing the ethyl acetate.After that, the concentration of the capsule solution was adjusted sothat the concentration of the solid components became 33%. In this way,a solution containing microcapsules was obtained. The median particlediameter of the microcapsules obtained was found to be 1.00 μm as aresult of measurement (by means of LA-700, manufactured by HoribaSeisakusho Co., Ltd.).

[0149] Further, a 25% aqueous solution of sodium dodecylbenzenesulfonate(trade name: NEOPELEX F-25, manufactured by Kao Corporation) in aproportion of 3.7 parts and a4,4′-bistriazinylaminostilbene-2,2′-disulfone derivative (trade name:Kaycall BXNL, manufactured by Nippon Soda Co., Ltd.) in a proportion of4.3 parts were added to 100 parts of the solution of microcapsules andthe resulting mixture was uniformly stirred. As a result, a solution (c)containing dispersed microcapsules was obtained.

[0150] <Preparation of a Dispersion Solution (c) of anElectron-Accepting Compound>

[0151] To 11.3 parts of the above-described aqueous solution ofphthalated gelatin were added 30.1 parts of ion-exchanged water, 15parts of 4,4′-(p-phenylenediisopropylidene)diphenol (trade name:Bisphenol P, manufactured by Mitsui Petrochemical Co., Ltd.), and 3.8parts of a 2% aqueous solution of sodium 2-ethylhexyl succinate and theresulting mixture was dispersed overnight in a ball mill. The dispersionsolution thus obtained had a concentration of solid components of 26.6%.

[0152] To 100 parts of the dispersion solution was added 45.2 parts ofthe aqueous solution of alkali-treated gelatin described above and theresulting mixture was stirred for 30 minutes. After that, theconcentration of solid components of the dispersion solution wasadjusted to 23.5% by the addition of ion-exchanged water. In this way, adispersion solution (c) containing an electron-accepting compound wasobtained.

[0153] <Preparation of a Coating Solution (c)>

[0154] The solution (c) containing microcapsules enclosing anelectron-donating dye precursor and the dispersion solution (c) of anelectron-accepting compound were mixed together such that weight ratioof the electron-accepting compound/the electron-donating dye precursorbecame 10/1. In this way, a coating solution (c) for cyan heat-sensitiverecording layer was obtained.

[0155] (4) Preparation of Coating Solution for Forming Interlayer

[0156] 100.0 parts of alkali-treated low-ion gelatin (trade name: No.750Gelatin, manufactured by Nitta Gelatin, Co., Ltd.), 2.857 parts of1,2-benzothiazoline-3-one (a 3.5% methanol solution, manufactured byDaitoh Kagaku Kogyosho Co., Ltd.), 0.5 parts of calcium hydroxide, and521.643 parts of ion-exchanged water were mixed together and made into asolution at 50° C. to thereby obtain an aqueous solution of gelatin forforming interlayer. 10.0 parts of the aqueous solution of gelatin forforming interlayer, 0.05 parts of sodium(4-nonylphenoxytrioxyethylene)butylsulfonate (a 2.0% aqueous solution,manufactured by Sankyo Kagaku Co., Ltd.), 1.5 parts of boric acid (a4.0% aqueous solution), 0.19 parts of an aqueous (5%) solution ofpolystyrenesulfonic acid (partially neutralized by potassium hydroxide),4.53 parts of a 4% aqueous solution of the following compound (J)(manufactured by Wako Pure Chemical Industries, Ltd.), and 0.67 parts ofion-exchanged water were mixed together. The mixture was used as thecoating solution for forming interlayer.

[0157] Compound J

[0158] 3:1 mixture of

(CH₂═CHSO₂CH₂CONHCH₂)₂—

[0159] and

CH₂(CH₂NHCOCH₂SO₂CH═CH₂)₂

[0160] (5) Preparation of a Solution for Forming Light TransmittanceControlling Layer

[0161] <Preparation of a Solution Containing Microcapsules Enclosing anUltraviolet Light Absorber Precursor>

[0162] 14.5 parts of[2-allyl-6-(2H-benzotriazole-2-yl)-4-t-octylphenyl]benzenesulfonate asan ultraviolet light absorber precursor, 5.0 parts of the followinghydrogen-donor (A-1), 1.9 parts of tricresyl phosphate, 5.7 parts ofα-methylstyrene dimer (tradename: MSD-100, manufactured by MitsuiChemical Co., Ltd.), and 1.26 parts of sodium dodecylbenzenesulfonate(trade name: NEOPELEX F-25, manufactured by Kao Corporation) werehomogeneously dissolved in 71 parts of ethyl acetate. To the resultingblend solution was added 54.7 parts of a xylylenediisocyanate/trimethylolpropane adduct (trade name: TAKENATE D-110N (a75% ethyl acetate solution), manufactured by Takeda Chemical Industries,Ltd.) as a capsule wall forming material and the resulting mixture washomogeneously stirred. In this way, a blend solution (VII) of anultraviolet light absorber precursor was obtained.

[0163] On the other hand, an aqueous solution of PVA for the solutioncontaining microcapsules enclosing an ultraviolet light absorberprecursor was prepared by blending 52 parts of itaconic acid-modifiedpolyvinyl alcohol (trade name: KL-318, manufactured by Kuraray Co.,Ltd.) with 532.6 parts of ion-exchanged water.

[0164] The blend solution (VII) of an ultraviolet light absorberprecursor was added to 516.06 parts of the aqueous solution of PVA forthe solution containing microcapsules enclosing an ultraviolet lightabsorber precursor and the resulting mixture was subjected toemulsifying dispersion by using a homogenizer (manufactured by NipponSeiki Seisakusho Co., Ltd.) at 20° C. Then, 254.1 parts of ion-exchangedwater was added to the emulsified solution and the solution washomogenized. Next, an encapsulation reaction was carried out by stirringthe solution at 40° C. for 3 hours. After that, 94.3 parts of AMBERLITEMB-3 (manufactured by Orugano Co., Ltd.) as an ion-exchange resin wasadded and the solution was stirred for another hour. The ion-exchangeresin was then eliminated by filtration and the concentration of thecapsule solution was adjusted so that the concentration of the solidcomponents became 13.5%. In this way, a solution containingmicrocapsules enclosing an ultraviolet light absorber precursor wasobtained. The median particle diameter of the microcapsules obtained wasfound to be 0.23±0.05 μm as a result of measurement (by means of LA-700,manufactured by Horiba Seisakusho Co., Ltd.).

[0165] <Preparation of a Coating Solution for Forming LightTransmittance Controlling Layer>

[0166] A coating solution for forming light transmittance controllinglayer was obtained by mixing 1000 parts of the solution containingmicrocapsules enclosing an ultraviolet light absorber precursor, 5.2parts of the following compound K (trade name: Megafac F-120, a 5%aqueous solution, manufactured by Dainippon Ink & Chemicals, Inc.), 7.75parts of a 4% aqueous solution of sodium hydroxide, and 73.39 parts ofsodium (4-nonylphenoxytrioxyethylene)butylsulfonate (a 2.0% aqueoussolution, manufactured by Sankyo Kagaku Co., Ltd.).

[0167] (6) Preparation of a Coating Solution for Protective Layer

[0168] <Preparation of a Polyvinyl Alcohol Solution for FormingProtective Layer>

[0169] A homogeneous polyvinyl alcohol solution for forming protectivelayer was obtained by mixing 160 parts of a vinyl alcohol/alkyl vinylether copolymer (trade name: EP-130, manufactured by Denki Kagaku KogyoKabushiki Kaisha), 8.74 parts of a blend solution of a sodiumalkylsulfonate and a polyoxyethylene alkyl ether phosphoric ester (tradename: NEOSCORE CM-57, a 54% aqueous solution, manufactured by TohoChemical Industry Co., Ltd.), and 3832 parts of ion-exchanged water andmaking the mixture into a homogeneous solution at 90° C. by allowing itto dissolve for one hour.

[0170] <Preparation of a Dispersion Solution of a Pigment for ProtectiveLayer>

[0171] A mixture comprising 8 parts of barium sulfate (trade name:BF-21F, having a barium sulfate content of 93% or more, manufactured bySakai Chemical Industry, Ltd.), 0.2 parts of an anionic specialpolycarboxylic acid type polymeric surfactant (trade name: POISE 532A (a40% aqueous solution), manufactured by Kao Corporation), and 11.8 partsof ion-exchanged water was dispersed in a Dyno mill to thereby prepare adispersion solution of barium sulfate. The median particle diameter ofthe dispersed particles was found to be 0.15 μm or less as a result ofmeasurement (by means of LA-910, manufactured by Horiba Seisakusho Co.,Ltd.).

[0172] A dispersion solution of a pigment for protective layer wasobtained by adding 8.1 parts of colloidal silica (trade name: SNOWTEXO(a 20% aqueous dispersion), manufactured by Nissan Chemical Co., Ltd.)to 45.6 parts of the dispersion solution of barium sulfate.

[0173] <Preparation of a Dispersion Solution of a Matting Agent forProtective Layer>

[0174] A dispersion solution of a matting agent for protective layer wasprepared by blending 220 parts of wheat starch (trade name: KOMUGIDENPUN S, manufactured by Shinshin Shokuryo Kogyo Co., Ltd.) with 3.81parts of an aqueous dispersion of 1-2-benzisothiazoline-3-one (tradename: PROXEL B.D, manufactured by I.C.I Limited) and 1976.19 parts ofion-exchanged water and uniformly dispersing these components.

[0175] <Preparation of a Blend Solution for Forming Protective Layer>

[0176] A blend solution for forming protective layer was prepared bymixing 40 parts of the compound K (trade name: Megafac F-120, a 5%aqueous solution, manufactured by Dainippon Ink & Chemicals, Inc.), 50parts of sodium (4-nonylphenoxytrioxyethylene)butylsulfonate (a 2.0%aqueous solution, manufactured by Sankyo Kagaku Co., Ltd.) 49.87 partsof the dispersion solution of a pigment for protective layer, 16.65parts of the dispersion solution of a matting agent for protectivelayer, and 48.7 parts of a dispersion solution of zinc stearate (tradename: HYDRIN F115, a 20.5% aqueous dispersion, manufactured by ChukyoYushi Co., Ltd.) in 1000 parts of the polyvinyl alcohol solution forforming protective layer.

[0177] (7) Support Coated with a Primer Layer

[0178] <Preparation of a Solution for Forming Primer Layer>

[0179] An aqueous solution of gelatin for primer layer was prepared bydissolving 40 parts of enzyme-decomposed gelatin (having an averagemolecular weight of 10,000, a viscosity of 1.5 mPa's (15 mP) inaccordance with PAGI, and a jelly strength of 20 g in accordance withPAGI) in 60 parts of ion-exchanged water at 40° C. while stirring.

[0180] On the other hand, 8 parts of water-swellable synthetic mica(having an aspect ratio of 1,000, trade name: SOMASIF ME100,manufactured by Cope Chemical Co., Ltd.) and 92 parts of water weremixed together and the resulting mixture was subjected to wet-dispersionby means of a Viscomill to thereby obtain a dispersion solution of micahaving an average particle diameter of 2.0 μm. To the dispersionsolution of mica was added water in an amount to obtain a micaconcentration of 5% and the resulting mixture was homogenized bystirring. In this way, a dispersion solution of mica that was aimed atwas prepared.

[0181] Next, 120 parts of water and 556 parts of methanol were added to100 parts of the above-described 40% aqueous solution of gelatin and theresulting mixture was sufficiently stirred at 40° C. To the solution wasadded 208 parts of the dispersion solution having a mica concentrationof 5% and the resulting mixture was sufficiently stirred. Next, 9.8parts of a 1.66% polyethylene oxide surfactant was added. After that,the solution obtained above was kept at 35 to 40° C. and 7.3 parts of agelatin hardener composed of an epoxy compound was added. In this way, a(5.7%) coating solution for forming primer layer was prepared.

[0182] <Manufacture of a Support Coated with a Primer Layer>

[0183] Wood pulp comprising 50 parts of LBPS and 50 parts of LBPK wasbeaten to 300 mL in Canadian Freeness by means of a disc refiner and wasadmixed with 0.5 parts of epoxidized behenic acid amide, 1.0 part ofanionic polyacrylamide, 1.0 part of aluminum sulfate, 0.1 parts of apolyamidepolyamine/epichlorohydrin, and 0.5 parts of cationicpolyacrylamide, each measured under absolute dry conditions and based onthe weight of the pulp. The pulp was fed to a long-mesh paper machine toproduce a base paper having a base weight of 114 g/m², which was thenadjusted to a thickness of 100 μm by calendering.

[0184] Next, after both sides of the base paper were subjected to acorona-discharge treatment, one of the sides of the base paper wascoated with a polyethylene resin to a resin layer thickness of 36 μm bymeans of a melt-extruder and thus a resin layer having a mat surface wasformed (this face is hereinafter referred to as the back). After that,the other side, i.e., the side opposite to the side having theabove-mentioned resin layer, of the base paper was coated with apolyethylene resin, which contained an amount of 10% of anatase-typetitanium dioxide and a tiny amount of ultramarine blue, to a resin layerthickness of 50 μm by means of a melt-extruder and thus a resin layerhaving a glossy surface was formed (this face is hereinafter referred toas the front). The polyethylene resin coating layer on the back wassubjected to a corona discharge treatment and then coated with ananti-static agent comprising an aqueous dispersion of aluminum oxide(trade name: Alumina Sol 100, manufactured by Nissan ChemicalIndustries, Co., Ltd.) and silicon dioxide (trade name: SNOWTEX O,manufactured by Nissan Chemical Industries, Co., Ltd.) in 1:2 weightratio such that a dry coating weight of 0.2 g/m² was obtained. Next, thepolyethylene resin coating layer on the front of the paper was subjectedto a corona discharge treatment and thereafter coated with theabove-described coating solution for forming primer layer such that acoating weight of mica of 0.26 g/m² was obtained. In this way, a supportcoated with a primer layer was obtained.

[0185] (7) Application of the Solutions for Forming Heat-SensitiveLayers

[0186] The support coated with a primer layer was coated consecutivelywith the solution (a) for forming yellow heat-sensitive recording layer,the solution for forming interlayer, the solution (b) for formingmagenta heat-sensitive recording layer, the solution for forminginterlayer, the solution (c) for forming cyan heat-sensitive recordinglayer, the solution for forming light-transmittance controlling layer,and the solution for forming protective layer, thus providing 7 layersin the order listed. The support coated with these layers was then driedat 30° C. and 30% RH and thereafter at 40° C. and 30% RH. In this way, amulticolor heat-sensitive recording material of Example 1 was obtained.

[0187] When applying the coating solutions, the coating weight of thesolution (a) for forming heat-sensitive recording layer was controlledsuch that the coating weight of the diazo compound (A) contained in thesolution (a) was 0.078 g/m² based on the solid component, the coatingweight of the solution (b) for forming heat-sensitive recording layerwas controlled such that the coating weight of the diazo compound (D)contained in the solution (b) was 0.206 g/m² based on the solidcomponent, and the coating weight of the solution (c) for formingheat-sensitive recording layer was controlled such that the coatingweight of the electron-donating dye (H) contained in the solution (c)was 0.355 g/m² based on the solid component.

[0188] Likewise, the coating weight of the solution for forminginterlayer between (a) and (b) was controlled such that the coatingweight based on the solid components was 2.39 g/m², the coating weightof the solution for forming interlayer between (b) and (c) wascontrolled such that the coating weight based on the solid componentswas 3.34 g/m² ₁ the coating weight of the solution for forminglight-transmittance controlling layer was controlled such that thecoating weight based on the solid components was 2.35 g/m², and thecoating weight of the solution for forming protective layer wascontrolled such that the coating weight based on the solid componentswas 1.39 g/m².

[0189] <Assessments>

[0190] The multicolor heat-sensitive recording material obtained wasexposed to irradiation from an ultraviolet lamp having a centralwavelength of emission of 420 nm and an output of 40W for 10 seconds andfurther exposed to radiation from an ultraviolet lamp having a centralwavelength of emission of 365 nm and an output of 40W for 15 seconds. Asa result, a yellow image was obtained. After that, the heat-sensitiverecording material was exposed for 96 hours to a radiation wavelength of420 nm at a radiation power of 0.9 W/m² using an irradiating apparatus(“WEATHEROMETER CI 65” manufactured by Atlas Electric Device Corp.)After the irradiation, the yellowness (Y value) of the white backgroundwas measured by means of X-Rite model 310 (manufactured by X-RiteIncorporated). The results are shown in Table 7.

Examples 2 to 4

[0191] Multicolor heat-sensitive recording materials of Examples 2 to 4were manufactured in the same way as in Example 1, except that thehydrogen donor (A-1) of the solution of microcapsules enclosing anultraviolet absorber precursor was replaced with the compounds,respectively, according to Table 7. The assessments were carried out inthe same way as in Example 1 and the results are shown in Table 7.

Comparative Example 1

[0192] The multicolor heat-sensitive recording material of ComparativeExample 1 was manufactured in the same way as in Example 1, except thatthe hydrogen donor (A-1) of the solution containing microcapsulesenclosing an ultraviolet absorber precursor was not used. The assessmentwas carried out in the same way as in Example 1 and the result is shownin Table 7. TABLE 7 Background density of non-image Hydrogen donor areaafter exposure Example 1 A-1 0.2 Example 2 A-2 0.21 Example 3 A-3 0.23Example 4 A-4 0.22 Comparative none 0.31 Example 1

What is claimed is:
 1. A heat-sensitive recording material containing anultraviolet light absorber precursor which forms an ultraviolet lightabsorber by being irradiated with light and a hydrogen donor.
 2. Theheat-sensitive recording material according to claim 1, wherein theultraviolet light absorber precursor is at least one kind selected fromthe compounds represented by the following general formulae (1) to (4):

wherein m represents 1 or 2; A represents —SO₂—R, —CO—R, —CO₂—R,—CONH—R, —POR₁R₂, —CH₂R₃, or SiR₁R₅R₆ in the general formula (1) where mis 1 and in the general formulae (2) to (4); A represents —SO₂R₇SO₂—,—CO—, —COCO—, —COR₇CO—, —SO₂—, or SO— in the general formula (1) where mis 2; X represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (3), and (4);X represents an alkylene group, —OR₇O—, or OCOR₇CO₂— in the generalformula (2); W represents a hydrogen atom, an alkyl group, an alkoxygroup, an aryl group, or a halogen atom in the general formulae (1),(2), and (4); W represents —OR₇O— or OCOR₇CO₂— in the general formula(3); Y represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (2), and (3);Y represents —OR₇O—, —OCOR₇CO₂—, —CH₂CH₂CO₂R₇OCOCH₂CH₂—,—CH₂CH₂OCOR₇CO₂CH₂CH₂—, or CH₂CH₂CON(R₈) R₇N(R₈)COCH₂CH₂— in the generalformula (4); and Z represents a hydrogen atom, a halogen atom, an alkylgroup, or an alkoxy group; with the proviso that R represents an alkylgroup or an aryl group; R₁ and R₂ each represents an alkoxy group, anaryloxy group, an alkyl group, or an aryl group; R₃ represents a phenylgroup bearing at least one nitro or methoxy group as a substituent; R₄,R₅ and R₆ each represents an alkyl group or an aryl group; R₇ representsan alkylene group or an arylene group; and R₈ represents a hydrogen atomor an alkyl group.
 3. The heat-sensitive recording material according toclaim 1, wherein the hydrogen donor has at least one group selected froman aromatic OH group, an aliphatic OH group, a heterocyclic OH group, anaromatic SH group, an aliphatic SH group, a heterocyclic SH group, anaromatic NH group, an aliphatic NH group, and a heterocyclic NH group.4. The heat-sensitive recording material according to claim 2, whereinthe proportion of the hydrogen donor is 1 to 1000% by weight relative tothe compound represented by any of the general formulae (1) to (4). 5.The heat-sensitive recording material according to claim 4, wherein theproportion of the hydrogen donor is 5 to 300% by weight relative to thecompound represented by any of the general formulae (1) to (4).
 6. Theheat-sensitive recording material according to claim 2, wherein thecoating weight of the compound represented by any of the generalformulae (1) to (4) is 0.1 to 1.5 g/m².
 7. The heat-sensitive recordingmaterial according to claim 2, wherein the heat-sensitive recordingmaterial further contains microcapsules and the compound represented byany of the general formulae (1) to (4) and the hydrogen donor areenclosed in the same microcapsule.
 8. The heat-sensitive recordingmaterial according to claim 7, wherein the particle diameters of themicrocapsules are 0.05 to 1.0 μm.
 9. The heat-sensitive recordingmaterial according to claim 2, wherein the heat-sensitive recordingmaterial further contains the compound represented by the followinggeneral formula (5):

wherein R_(a) to R_(d) each represents a hydrogen atom, an unsubstitutedor substituted alkyl group, an alkoxy group, an ester group, an arylgroup, or a halogen atom.
 10. The heat-sensitive recording materialaccording to claim 9, wherein the content of the compound represented bythe general formula (5) is 0.05 to 20 times the content of the compoundrepresented by any of the general formulae (1) to (4).
 11. Aheat-sensitive recording material comprising a support, a photo-fixingtype heat-sensitive recording layer, an interlayer, a protective layer,and a light-transmittance controlling layer, each provided on thesupport, wherein any one of the layers contains an ultraviolet lightabsorber precursor and a hydrogen donor.
 12. The heat-sensitiverecording material according to claim 11, wherein the ultraviolet lightabsorber precursor is at least one kind selected from the compoundsrepresented by the following general formulae (1) to (4):

wherein m represents 1 or 2; A represents —SO₂—R, —CO—R, —CO₂—R,—CONH—R, —POR₁R₂, —CH₂R₃, or SiR₄R₅R₆ in the general formula (1) where mis 1 and in the general formulae (2) to (4); A represents —SO₂R₇SO₂—,—CO—, —COCO—, —COR₇CO—, —SO₂—, or SO— in the general formula (1) where mis 2; X represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (3), and (4);X represents an alkylene group, —OR₇O—, or OCOR₇CO₂— in the generalformula (2); W represents a hydrogen atom, an alkyl group, an alkoxygroup, an aryl group, or a halogen atom in the general formulae (1),(2), and (4); W represents —OR₇O— or OCOR₇CO₂— in the general formula(3); Y represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (2), and (3);Y represents —OR₇O—, —OCOR₇CO₂—, —CH₂CH₂CO₂R₇OCOCH₂CH₂—,—CH₂CH₂OCOR₇CO₂CH₂CH₂—, or CH₂CH₂CON(R₈)R₇N(R₈)COCH₂CH₂— in the generalformula (4); and Z represents a hydrogen atom, a halogen atom, an alkylgroup, or an alkoxy group; with the proviso that R represents an alkylgroup or an aryl group; R₁ and R₂ each represents an alkoxy group, anaryloxy group, an alkyl group, or an aryl group; R₃ represents a phenylgroup bearing at least one nitro or methoxy group as a substituent; R₄,R₅, and R₆ each represents an alkyl group or an aryl group; R₇represents an alkylene group or an arylene group; and R₈ represents ahydrogen atom or an alkyl group.
 13. The heat-sensitive recordingmaterial according to claim 11, wherein the hydrogen donor has at leastone group selected from an aromatic OH group, an aliphatic OH group, aheterocyclic OH group, an aromatic SH group, an aliphatic SH group, aheterocyclic SH group, an aromatic NH group, an aliphatic NH group, anda heterocyclic NH group.
 14. The heat-sensitive recording materialaccording to claim 11 which has a plurality of the photo-fixing typeheat-sensitive recording layers.
 15. The heat-sensitive recordingmaterial according to claim 14 which has a photo-fixing typeheat-sensitive recording layer containing a diazonium salt compoundwhose maximum absorption wavelength is 365+40 nm and a coupler whichreacts with the diazonium salt compound to develop a color and aphoto-fixing type heat-sensitive recording layer containing a diazoniumsalt compound whose maximum absorption wavelength is 425±40 nm and acoupler which reacts with the diazonium salt compound to develop acolor.
 16. The heat-sensitive recording material according to claim 14which has a photo-fixing type heat-sensitive recording layer containinga diazonium salt compound whose maximum absorption wavelength is lessthan 380 nm and a coupler which reacts with the diazonium salt compoundto develop a color and a photo-fixing type heat-sensitive recordinglayer containing a diazonium salt compound whose maximum absorptionwavelength is more than 390 nm and a coupler which reacts with thediazonium salt compound to develop a color.
 17. A multicolorheat-sensitive recording material which comprises a support and aplurality of photo-fixing type heat-sensitive recording layers providedon the support and contains an ultraviolet light absorber precursor anda hydrogen donor, wherein the photo-fixing type heat-sensitive layersdevelop yellow, magenta, and cyan, respectively, so that full-colorrecording can be carried out.
 18. The heat-sensitive recording materialaccording to claim 17, wherein the ultraviolet light absorber precursoris at least one kind selected from the compounds represented by thefollowing general formulae (1) to (4):

wherein m represents 1 or 2; A represents —SO₂—R, —CO—R, —CO₂—R,—CONH—R, —POR₁R₂, —CH₂R₃, or SiR₄R₅R₆ in the general formula (1) where mis 1 and in the general formulae (2) to (4); A represents —SO₂R₇SO₂—,—CO—, —COCO—, —COR₇CO—, —SO₂—, or SO— in the general formula (1) where mis 2; X represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1) (3), and (4);X represents an alkylene group, —OR₇O—, or OCOR₇CO₂— in the generalformula (2); W represents a hydrogen atom, an alkyl group, an alkoxygroup, an aryl group, or a halogen atom in the general formulae (1),(2), and (4); W represents —OR₇O— or OCOR₇CO₂— in the general formula(3); Y represents a hydrogen atom, an alkyl group, an alkoxy group, anaryl group, or a halogen atom in the general formulae (1), (2), and (3);Y represents —OR₇O—, —OCOR₇CO₂—, —CH₂CH₂CO₂R₇OCOCH₂CH₂—,—CH₂CH₂OCOR₇CO₂CH₂CH₂—, or CH₂CH₂CON(R₈)R₇N(R₈)COCH₂CH₂— in the generalformula (4); and Z represents a hydrogen atom, a halogen atom, an alkylgroup, or an alkoxy group; with the proviso that R represents an alkylgroup or an aryl group; R₁ and R₂ each represents an alkoxy group, anaryloxy group, an alkyl group, or an aryl group; R₃ represents a phenylgroup bearing at least one nitro or methoxy group as a substituent; R₄,R₅, and R₆ each represents an alkyl group or an aryl group; R₇represents an alkylene group or an arylene group; and R₈ represents ahydrogen atom or an alkyl group.
 19. The heat-sensitive recordingmaterial according to claim 17, wherein the hydrogen donor has at leastone group selected from an aromatic OH group, an aliphatic OH group, aheterocyclic OH group, an aromatic SH group, an aliphatic SH group, aheterocyclic SH group, an aromatic NH group, an aliphatic NH group, anda heterocyclic NH group.
 20. The multicolor recording material accordingto claim 18, wherein the compound represented by any of the generalformulae (1) to (4) and the hydrogen donor are contained in the samelayer.